1. Field of the Invention
This invention relates to hollow cellulose fibers adapted for use in artificial dialysis, a method for making the same, and a fluid processing apparatus using the same.
2. Discussion of the Prior Art
The modern treatment for renal disease has marked a great advance due to the development of artificial kidney apparatus utilizing dialysis and ultrafiltration. Those patients whose kidney function is damaged or lost can survive for 10 years or more by virtue of artificial kidney apparatus. Nevertheless, they suffer from various complicating diseases inherent to long-term chronic renal insufficiency.
To avoid such complicating diseases, various attempts have been made to remove middle to high molecular weight substances from blood. Since the discovery that carpal tunnel syndrome, one of complicating diseases, is caused by the presence of .beta..sub.2 -microglobulin (molecular weight 11,800) in blood, efforts have been focused on the effective removal of .beta..sub.2 -microglobulin from blood.
Dialysis membranes are often used for removing .beta..sub.2 -microglobulin from blood. One example is disclosed in Japanese Patent Application Kokai No. 109871/1988 "Hemodialysis Membrane." The disclosed hemodialysis membrane is characterized by a total protein permeability of up to 0.2% and a percent removal of .beta..sub.2 -microglobulin of at least 5%. Upon hemodialysis, the hemodialysis membrane can selectively remove .beta..sub.2 -microglobulin from various proteins in blood.
However, the previously proposed hemodialysis membrane has several drawbacks. First, the membrane which is most preferably formed of polymethyl methacrylate (PMMA) tends to adsorb .beta..sub.2 -microglobulin. As a consequence, the dialysis membrane is contaminated to lose its function with a lapse of service time. Also the membrane lowers its ultrafiltration factor with a lapse of time due to clogging.
Secondly, the previously proposed dialysis membrane removes excess amount of water from blood when assembled in an artificial dialyzer designed to carry out ultrafiltration, that is, to remove water from blood utilizing the differential pressure between the blood side and the dialysate side (under negative pressure). Accordingly, an increased amount of fluid such as physiological saline must be replenished against the general demand that the amount of physiological saline admitted into the body should be controlled as small as possible. An increased amount of such complemental fluid, of course, adds to the expense. Although it is possible to control the pressure of dialysate in the dialyzer for reducing the amount of water removed using a UFR controller, there often occurs a phenomenon known as back-filtration that pyrogen in the dialysate migrates into blood, imposing a danger to the patient.